1. Field of the Invention
The present invention is directed to a watercraft, and more particularly to an improved air induction system employed in an engine of a watercraft.
2. Description of the Related Art
Personal watercraft have become increasingly popular in recent years. This type of watercraft is sporting in nature; it turns swiftly, it is easily maneuverable, and accelerates quickly. A personal watercraft today commonly carries one rider and up to three passengers. Typically, the rider and passengers sit on a straddle-type seat that is formed by the hull of the watercraft. The straddle-type seat is generally aligned with the longitudinal axis of the hull.
The space beneath the straddle-type seat is usually used as an engine compartment for supporting and housing the engine within the watercraft. The engine is preferably arranged within the engine compartment so that the crankshaft of the engine is aligned with the longitudinal axis of the watercraft. With the engine arranged as such, the crankshaft of the engine may be directly connected to an output shaft for driving a propulsion unit. Additionally, such an arrangement allows the engine to be arranged at least partially within the seat pedestal. Arranged as such, the engine and the seat pedestal form a compact unit. During operation, the rider and any passengers straddle the seat, and thus a portion of the engine while they are seated on the straddle-type seat. This hull shape requires the engine to be in close spacing with the passengers during operation, thus allowing the overall size of the watercraft to remain small, resulting in a compact and highly maneuverable watercraft.
Although these watercraft are generally highly maneuverable and are used in a sporting manner, there is an interest in reducing the noise generated by this type of watercraft. One part of the watercraft propulsion system that can generate noise is the induction system of the engine. For the most part, the induction systems used for this type of watercraft have been designed primarily to ensure adequate air induction and at least some filtration of the inducted air. Less effort has been given, however, to the silencing of the induction system.
In response to the noise generated by two-cycle engines, which are commonly employed in personal watercraft, certain recreational facilities have banned the operation of two-cycle engine powered watercraft. Such bans have resulted in a decrease in popularity of personal watercraft powered by two-cycle engines.
Obviously, it is necessary for the induction system to be able to ingest an adequate flow of air for maximum engine performance. In many instances, the induction systems previously proposed for watercraft have not recognized the advantages of using a tuning arrangement on the intake side of the engine. One reason for this is that the space available in an engine compartment of a personal watercraft generally does not afford room for various types of intake tuning systems. Although it has been known that a large intake air box will prevent the generation of loud noises in the induction system and will generate a smooth flow of air into the combustion chambers, the small space available in the hulls of small watercraft have prevented the use of large air boxes. In addition, the space available makes it difficult to tune the induction system to improve intake efficiency.
For example, a large air box mounted so as to feed the intake runners arranged along one side of an engine within the engine compartment of a watercraft will tend to attenuate induction noises and improve intake efficiency. However, as discussed above, engines are preferably arranged within the seat pedestals of personal watercraft such that their crankshaft is aligned with the longitudinal axis of the watercraft. As such, the intake runners open at a side of the engine body, facing an inner wall of the seat pedestal. Therefore, the size of the intake air box affects the overall width of the engine. If a large intake air box is used, the overall width of the engine is increased.
Since the rider and any passengers straddle the seat pedestal and engine during operation, the overall width of the engine is limited to that which would fit within a straddle-type seat pedestal. If the pedestal is too wide, a rider cannot comfortably sit on the seat pedestal during operation of the watercraft. Therefore, any portions of the engine mounted along either side of the engine body, such as the induction system, should be small enough such that the engine can still fit within the seat pedestal defining an engine compartment of the watercraft.
Additionally, because of its sporting nature, personal watercraft are oftentimes laid on their side or are flipped over by advanced riders during use. It thus is also important that the induction system be designed in such a way to inhibit ingesting water, which may be present in the engine compartment, into the engine through the induction system.